The invention relates to improvements in electric hair drying and hair styling apparatus (hereinafter called hair dryers), and more particularly to improvements in hair dryers of the type wherein an air flow concentrating nozzle is connectable to and detachable from the air discharging outlet of the housing.
A portable hair dryer normally comprises a hollow housing with an inlet and an outlet, a motor-driven impeller which serves as a means for inducing the flow of air from the inlet to the outlet when the hair dryer is in use, and normally adjustable means for heating the air stream between the inlet and the outlet. This ensures that the temperature of the air stream issuing from the housing by way of the outlet suffices for desired drying or styling of the hair of a person using the hair dryer or of a customer in a beauty salon. It is also known to furnish a portable hair dryer with a detachable air flow concentrating nozzle which can be connected to or detached from the housing and, when in use, serves to reduce the cross-sectional area of the stream of heated air which issues from the hair dryer. The controls for the electric motor which drives the impeller and the means for selecting the output of the heating element or elements of the heating means are or can be installed in and on a hollow handle which is normally provided to facilitate manipulation of the hair dryer and usually extends at an obtuse angle to the direction of air flow from the inlet to the outlet of the main portion of the housing.
The output of a modern hair dryer is rather high, often well in excess of 1000 watts, and the trend is toward still higher outputs. Such hair dryers operate quite satisfactorily, as long as heated air is permitted to escape through the relatively large outlet of the housing. However, the temperature of outflowing heated air is likely to reach unacceptably high values if the selected output is 1000 watts or more and the user cf the hair dryer decides to install the nozzle in front of the outlet of the housing. Under such circumstances, the temperature of outflowing heated air can reach and even considerably exceed a value (normally between 120.degree. and 130.degree. C.) at which hot air is likely to singe or actually burn the hair.
Attempts to overcome the drawbacks of the aforediscussed hair dryers include the provision of a temperature monitoring device which is installed in or close to the outlet of the housing and serves to generate signals which are used to reduce the output of the heating element or elements when the monitored temperature is too high so that hot air issuing by way of the nozzle would be likely to damage or burn the hair and/or cause injury to the person. It is also known to adjust the maximum output which can be achieved when the monitoring device transmits a signal. Such monitoring devices are effective and useful; however, the utilization of monitoring devices necessitates the installation of numerous electronic components or modules which contribute significantly to the initial and maintenance cost of the hair dryer. Moreover, the circuits embodying temperature monitoring devices are prone to malfunction.